Nascar Glosary

AERO PUSH

When following another vehicle closely, the airflow off the lead vehicle does not travel across the following one(s) in a normal manner. Therefore, downforce on the front of the trailing vehicle(s) is decreased and it does not turn in the corners as well, resulting in an “aero push.” This condition is more apparent on the exit of the turns. AERODYNAMIC DRAG A number that is a coefficient of several factors that indicates how well a race vehicle will travel through the air and how much resistance it offers. Crewmen work to get the best “drag horsepower” rating they can, determining how much horsepower it will take to move a vehicle through the air at a certain mile-per-hour rate. At faster speedways teams strive to get the lowest drag number possible for higher straightaway speeds.

AIR PRESSURE

With the advent of radial tires with stiffer sidewalls, changing air pressure in the tires is used as another setup tool that is akin to adjusting spring rates in the vehicle’s suspension. An increase in air pressure raises the “spring rate” in the tire itself and changes the vehicle’s Hankling characteristics. If his race vehicle was “tight” coming off a corner, a driver might request a slight air pressure increase in the right rear tire to “loosen it up.”

CAMBER

Camber addresses the angle at which a tire makes contact with the track surface. “Positive camber” indicates the angle of the tire is tilted away from the vehicle’s centerline while “negative camber” indicates the tire is tilted toward the centerline. A typical oval track setup would have positive camber in the left front and negative camber in the right front to help the vehicle make left-Hank turns.

DOWNFORCE

The air pressure traveling over the surfaces of a race vehicle creates “downforce” or weight on that area. In order to increase corner speeds teams strive to create downforce that increases tire grip. The tradeoff for increased corner speeds derived from greater downforce is increased drag that slows straightaway speeds.

LOOSE

(Also referred to as “free” or “oversteer.”) A condition created when the back end of the vehicle wants to overtake the front end when it is either entering or exiting a turn. In qualifying mode teams walk a fine line creating a setup that “frees the vehicle up” as much as possible without causing the driver to lose control.

MARBLES

(Also referred to as “loose stuff.”) Bits of rubber that have been shaved off tires and dirt and gravel blown to the outside of a corner by the wind created by passing vehicles comprise the “marbles” that are often blamed by drivers for causing them to lose control.

PUSH

(Also referred to as “tight” or “understeer.”) “Push” is a condition that occurs when the front tires of a vehicle will not turn crisply in a corner. When this condition occurs, the driver must get out of the throttle until the front tires grip the race track again.

RESTRICTOR PLATE

An aluminum plate that is placed between the base of the carburetor and the engine’s intake manifold with four holes drilled in it. The plate is designed to reduce the flow of air and fuel into the engine’s combustion chamber, thereby decreasing horsepower and speed.

ROOF FLAPS

These flaps are sections at the rear of a race vehicle’s roof that are designed to activate, or flip up, if the air pressure flowing across them decreases. In the case of a vehicle turning backwards, the tendency for an uninterrupted flow of air is to create lift. The roof flaps are designed to disrupt that airflow in attempt to keep the vehicle on the ground.

SPOILER

(Also referred to as a “blade.”) The spoiler is a strip of aluminum that stretches across the width of a race vehicle’s rear decklid. It is designed to create downforce on the rear of the vehicle, thereby increasing traction. However, the tradeoff, again, is that more downforce equals more aerodynamic drag, so teams attempt, particularly on qualifying runs, to lay the spoiler at as low an angle as possible to “free up” their vehicles for more straightaway speed.

STAGGER

Stagger is a concept that has largely been eliminated with the use of radial tires. It refers to the difference in tire circumference between the left- and right-side tires on the vehicle. Typically, the left-side tires would be a smaller circumference than the right-side tires to “help” the vehicle make left-Hank turns.

TRACK BAR

(Also referred to as a “Panhard bar.”) This bar locates the vehicle’s rear end housing from left-to-right under it. In calibrating the vehicle’s “suspension geometry,” raising or lowering the track bar changes the rear roll center and determines how well it will travel through the corners. During races, this adjustment is done through the rear window using an extended ratchet. Typically, lowering the track bar will “tighten” the vehicle and raising the track bar will “loosen” it.

VALANCE

(Also referred to as “front air dam.”) This is the panel that extends below the vehicle’s front bumper. The relation of the bottom of the valance, or its ground clearance, affects the amount of front downforce the vehicle creates. Lowering the valance creates more front downforce.

WEDGE

Refers to the relationship from corner-to-corner of the weight of the race vehicle. Increasing the weight on any corner of the vehicle affects the weight of the other three corners in direct proportion. Weight adjustments are made by turning “weight jacking screws” mounted on each corner with a ratchet. A typical adjustment for a “loose” car would be to increase the weight of the left rear corner of the vehicle, which decreases the weight of the left front and right rear corners and increases the weight of the right front. A typical adjustment for a “tight” vehicle would be to increase the weight of the right rear corner, which decreases the weight of the right front and left rear and increases the weight of the left front.

WIND TUNNEL

A structure used by race teams to determine the aerodynamic efficiency of their vehicles, consisting of a platform on which the vehicle is fixed and a giant fan to create wind currents. Telemetry devices determine the airflow over the vehicle and its coefficient of drag and downforce.

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